Stepper motor Not rotating freely

Recently get a Old step syn nema 23(Made in Japan)stepper motor.
One of my nema 23 stepper motor is so tight and cannot swing it with my hand too tight(chucked with 3 jaw chuck and can swing it with hand).I think it will burn my stepper driver with this condition.
I open the covers and check where is the problem.
Bearings are good and inspected my dad who is experienced 30 years of manual all round machinist.
Once I attached the rotor with stator without bearings it binds.
I machined to reduce diameter of rotor few hundreds of mm.
but no 100% good.now it can rotate it by pliers and sometimes with hand.

Can I work with this or should I replace another?

DinukaShehan wrote: Can I work with this or should I replace another?

No you can not, the stepper motors should not be opened, they will loose the magnetic field while you are getting the rotor out, so it will not have any torque any more.
You can open ONLY the back cover without destroying it.

How to count steps of stepper motor without opened?

To know 1.8 degree or another one?

they will loose the magnetic field while you are getting the rotor out

Any technical data or proofs do you have about this?

Please ask GOOGLE your questions and you will find many answers.

DinukaShehan wrote:

they will loose the magnetic field while you are getting the rotor out

Any technical data or proofs do you have about this?

Yes i do, two motors with no torque.
They are magnetised after they are put together in the factory, so fully assembled.

How to calculate number of steps of stepper motor without removing the covers?
Note there are no label or markings on this motor.

Attach a 20 to 30 cm stick with glue to its shaft so you can actually measure the angle it moves.
Or make a line in the shaft and body of motor and try to count the steps while slowly rotating the shaft.
The first is more precise the longer the stick.